Brake



March 11, 1941. s, F. KARST ET AL BRAKE Filed Dec. 27, 1938 3 Sheets-Sheet l Mdm F/UPZEH E Manuf March 11, 1941. s. F. KARsT ET A1.

BRAKE Filed Dec. 27, 1958 3 Sheets-Shee'l 2 MD/eu* EyZI/EEZQP F. Kars? F/Urzsn E M5270? @Ma/mak;

March 1l, 1941. A s. F. KARsT ETAL 2,234,257

BRAKE Filed Dec. 27, 1938 3 Sheets-Sheet 5 QLD l 1 W [l PW17 EyZx/Esigr T Kars? Finnen F. MENU?" www Patented Mar. 11, 1941 UNITED STATES PATENT OFFICE Wis.,

assignors of one-third to Thomas W.

Meiklejohn, Fond du Lac, Wis. Application December 27, 1938, Serial No. 247,892

11 Claims.

This invention relates to brakes, and refers particularly to automobile brakes.

Automobile brakes are nowsubstantially always of the internal expansion type in which aplurality of brake shoes are arranged to be expanded. or moved outwardlyinto braking engagement with the inner cylindrical face off the revolving brake drum. The actual expansion of the brake shoesinto. engagement with the brake drum may be effected either mechanically or hydraulically.

In all instances, however, the construction of the brakes has been such in the past that the. brake lining would wear unevenly, not only with respect to diierent portions `of the same shoe, but the primary shoe would have its lining. completely worn beforev the lining on the secondary shoe showed any real wear.

This uneven wear of the brake lining prevalent in brakes heretofore in use was brought about by the. fact that only the primary shoehad a wrapping action during forward travel of the vehicle while the secondary shoe had` a wrapping action only during backward travel of the vehicle.

The present invention, thereforahas as one of its objects to provide a. brake so constructed that both primary andl secondary shoes have av Wrapping action at all times thus assuring uniform wear of the brake lining, not only as to all portions of each shoe, butV on both shoes alike.

Another object of this invention is to provide a brake wherein proper clearance between the lining and the drum is maintained automatically as the lining wears so as to entirely obviate the need forl adjustments of any' character.

Another object of this invention is to provide means for automatically taking up any' wear which may occur in the actuating mechanism of the brake so that there will be no play' nor loose' fitting parts with their consequent rattling and unsatisfactory braking action.

Still another object of this invention is to provide an improved brake of the character def scribed whereby the advantages stated are obtained without deviating from the general accepted design of brakes of this character so that the incorporation of these improvements canv be effected with little or no additional cost and Without altering the present methods of manufacturing such brakes.

With the above and other objects in view which will appear as the. description proceeds, this irrvention resides` in thenovel construction, combination andA arrangement of parts substantially asl (Cl. 18S- 78) hereinafter described, and more' particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed in accordance with the` best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a vertical sectional view through a brake embodying this invention, said view being taken on the plane of the line I--I of Figure 3, and illustrating the left front wheel ofl an automobile;

Figure 2 is a View similar to Figure 1, but illustrating the parts in their positions at the time the brake is applied, said view having portions thereof broken away to more clearly illustrate details of construction;

Figure 3 is a vertical cross sectional view taken' through Figure 1 on the plane of the line 3 3;

Figure 4 isa perspective view of one ofthe brake shoe actuating' elements;

, Figure 5 isa perspective view showing the mechanism by which proper positioning of the brake shoes is automatically eiected; and

Figures' 6 and '7 are diagrammatic views of this same mechanism, illustrating its manner of operation.

Referring noW particularly to thev accompanying drawings in which like numerals' indicate like parts throughout the several views, the numeral 5 designates the hub portion of the left front wheel of an automobile, journalled on a spindle 6 by bearings (not shown). The spindle 6 is carried by a yoke 'I by which the entire wheelV is mounted on the front axle (not shown) for steering movement.

The hub portion 5, as is customary, is adapted to have a wheel (not shown) bolted thereto and is further provided with the customary brake drum 8.

Inside the brake drum is the brake mechanism. It is carried by a back plate- 9 xed to the yoke '1, and part thereof, as' will be later described,` is mounted on a large cylindrical bearing l0 fixed to the back plate coaxially with the spindle 6.

The brake mechanism comprises two brake als;

shoes, a primary shoe Il and a secondary shoe erally by rivets, and a flat radial web I5 extendin g inwardly from the arcuate flange I4.

These shoes are loosely held in position inside the brake drum by spring retainers I6, which are anchored to the back plate 9 and yieldingly draw the shoes against the outer face thereof, the back plate having outwardly directed projections I1 at spaced intervals with which the inner edges of the brake abut. f

EachA brake shoe has a toe portion I8 and a heel portion I9, and the heel portion of the primary shoe and the toe portion of the secondary shoe have inward projections 2!) adapted to engage the outer cylindrical surface of the bearing I0. The toe portion of the primaryk shoe and the heel portion of the secondary shoe have ex-' These tensions 2| directed toward each other. extensions are alike and each is composed of spaced apart plates between which a wedge-like expander 22 is positioned.

I he sides of this expander engage rollers 23 also mounted in the space between the plates forming the extensions 2l.

Hence, by an outward radial motion Vof the wedge-like expander 22, the adjacent ends of the brake shoes are spread apart. Such outward spreading of these ends of the brake shoes is yieldingly resisted by tension springs 24, each having one end hooked onto one brake shoe and its opposite end engaged with a pin 25 which is anchored to the back plate 9, notches in the ends of-the brake shoe extensions andan opening in the expander accommodating the pin 25.

Outward radial motion is imparted to the expander to positively expand the brakey shoes, by means of a lever 2S pivoted as at 21'on a stud carried by the back plate, and engaging the expander througha swivel connection 28. One end of this lever has a cable 29 attached to it which passes through an appropriate hole in the back plate andleads to the pedal actuated mechanism sothat depression of the pedal applies al pull on the cable in the customary manner. p' l The lever and ,the cable are `returned to their normal positions by a spring 3i), one end of which engages the end of the lever opposite its connection with the cable and the other end of which is hooked into a hole 3I in the web I5 of the secondary shoe.

Obviously, the mechanical means described for actuating the expander may be supplanted by a hydraulic mechanism without deviating fromthe invention.

To the extent thus far described, the brake mechanism is' more or less vconventional for through the action of the positive expander 22, the toe portion I8 o-f the primary shoe and the heel portion I9 of the secondary shoe are pushed out into contact with the revolving brake drum. The primary shoe would then act with a Wrap` ping eiect, but the secondary shoe would merely drag and be more or less ineffective.

With`this invention, however, actuation of the*` expander 22 not only engages the toe portion of the primary .and the heel portion of the sec-` ondary shoewiththe drum, but also pushes out the toe portionof the secondary shoe, which is important, and the heel portion of the primary shoe; Consequently, the entire braking surface is applied to the drum at the same time-and both e shoes have a Wrapping action.

This is brought about by the provision of two motion transmitting rings 32 mounted for rotation on the bearing I0,one toapply an outward pressure on the toe portion of the secondary shoe in a manner to be hereinafter and the other to apply an outward pressure on the heel portion of the primary shoe.

The two motion transmitting ringsl are identical, and each has a lug 33 welded to one side thereof for engagement with the portionV 20 of the shoes, and a disc 34 eccentrically mounted on the ring by a stud 35. A torsion spring 36, having one end anchored to the stud and its other end hooked about ay pin 31 on the disc, yieldingly tends to turn the disc in one direction, for a purpose to be hereinafter described. Preferably, although not necessarily, the disc is spool-shaped with flanges 38 on its opposite sides.

The peripheries of the discs 34 engage actuator Varms'. 39 formed as integral parts of the web-s I5 of both shoes and the relationship of these parts is such that the torsion springs 36 at all times urge their long radii portions toward the actuator arms 39 to take up play between the parts,

more fully described. 1

The rings 32 are applied to the bearings I D ink reversed order. Thatvis, one ring which is positioned between the plane ofthe webs I5 of the brake shoes and the back plate 9 is applied with its lug and eccentric disc facing outwardly to vbe in vline with the plane of the webs I5; whereas the other ring is applied in the opposite manner with its, lug and eccentric disc facing inwardly;r It will thus be seen that upon expansion of the brake shoes by the expander 25, rotation will be simultaneously imparted to both of the rings32 in opposite directions, whereby the oppositeends of the shoes will likewise be expanded or spread apart through the movement apart of the lugs 33.

Expansion of these latter ends of the shoes is yieldingly opposed by tension springs 40, each` having one end hooked into the hole 3l of each brake shoe and its opposite end engaged over a fixed pin 4I carried by the back plate. These springs, like the springs 24, return vthe shoes to their inactive positions upon release of the brake actuating pedal (notshown). Y I

` The springs 40, as stated, yieldingly draw the heel of the primary shoe and the -toe of the secondary shoe together. 'Ihe extent to which these portions of the shoes are drawn 4together is limitedl by an automatically adjustable spacer 43.

' This spacer comprises a pair of complementary wedge ymembers 44 and v45,the outer ends of which are bifurcated to embrace the adjacent end portionsv of the brake shoe webs 'to which they are attached by pins 46. The side edges of the members and 45 are inclined, and the adjacent edges of the two members are in engagement so that by movement apart the width across the, engaging portions of the wedge members is reduced, vand by movement together, it is increased. l y

These engaging portions ofY the wedge members 'are embraced by a collar or band 41, the edge walls of `which are tapered withr the narrow width `facing the wedge member 45. The composite width of the engaging portions of the wedge members isv correspondingly tapered so that by forcing the collar or sleeve 41 ltoward the wedge member44, the wedge members can be releasably locked in different relative positions.

To maintain the sleeve or collar in i-ts operative position, a compression spring 48 encircles the wedge'member 45 between the. edgeV of the brake shoev withv which the wedge member 45 is connected an'd the adjacent narrow end of. v.the

collar or band. 41., a washer 49 being placed between the spring andi the band to provide a seat for the spring.

The connections between the bifurcated ends of the wedge members and the brake shoes have a degree of play or clearance by virtue of the fact that the holes 50 in the webs of the brake shoes through which the pins 46 pass are slightly larger than the pins. This relationship is illustrated in exaggerated form in Figures 6 and 7.

It isy this clearance or play between the pins and the holes in the brake shoe webs which'automatically maintains the proper clearance between the brake linings and the brake drum.

Thefmanner in which it is accomplished can be bestv understood from reference to Figures 6 and 7', the former of which shows the parts in the positions they occupy when the brake is disengaged, and the latter shows the` parts in the positions they occupy when the brake is engaged.

As illustrated in these views, when the brake is released and the springs 40 are free to draw the brake shoes together, the pins engage the outermost edges of the holes 5B with reference to a line drawn through and connecting the axes of the pins, and when the brake is engaged, that is, the shoes are expanded or spread apart, then the pins engage the inner edge portions of the holes 50, or at least approach the same.

The effective length ofthe spacer remains unchanged until the brake linings wear and it is necessary to spread the shoes farther apart to effect proper engagement of the brake.

In that event, the eiIec-tive length of the spacer will be increased by the engagement of the inner edges of the holes with the pins 46 and the relative outward motion of the brake shoes. When the brake is released after automatic adjustment of the length of the spacer, the spacer length remains as readjusted where it is held by the locking action of the wedges and the collar or band 4l, and the brake shoes come together an extent sufficient to engage the pins 46 with the e inner edges of the holes 50.

In this new position of adjustment, the brake shoes are, of course, farther apart than they were initially, but the important result is that the clearance between the brake lining and the surface of the drum at all times remains constant, being determined solely by the extent of play which the pins 4B have in the holes 5D.

Contact. is always maintained between the lugs. 331 and the edges of the brake drum webs which they engage by the automatic take-up comprising the eccentric discs 34. As stated,

when the brake is released, the shoes are drawnk together by the springs 40 and 24, carrying the lugs 33 with them and revolving the rings 32 as required.

Inl the event of readjustment of the spacing between the brake shoes, in the manner olescribed, which means that the lugs 33' will not be carried back to their initial positions, play would result between the actuator arms 39 and the discs 34, except for the torsion springs 36, which, as previously stated, constantly tend to turn the discs 34l in a direction to swing their large radii portions toward the arms 39. Thus, through the medium of the eccentrically mounted discs i4. and their torsion springs 36, play is automatically Itaken up between the parts by which the ends cf the shoes opposite the expander are actuated.

The nanges 38 on the eccentrically mounted.

discsv engage over. the side edges of the actuator arms'. 39:' and thus. hold the discs against lateral displacement with respect to the arms 39. Lateral displacement of they lugs 33 with respect to the web portions 20: which they engage is precluded by having' the rings 32 engage opposite sides of the web portions. 2i! where they are held. by suitable abutments carried by the bearing IQ, such as` cotter pins 5| passing through the wall of the bearing i0 in front of the foremost disc 32 and projections 52 struck from the back plate 9.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent that this invention provides a very material improvement over past brake constructions, and that it assures uniform wear of the lining and entirely obviates the need for adjustment.

It will also be apparent that the conventional and accepted design for internal expansion brakes has been retained substantially in its entirety, and that the improvements and advantagesV of this invention are obtained with but fewchanges in this accepted design so that'the cost of manufacture is not seriously increased.

What we claim` as our invention is:

1. In a brake or" the character described: a rotatablebrake drum; a pair of brake shoes inside the drum and having braking surfaces engageable with the inner face of the drum; means loosely holdin-g said brake shoes in position and permitting movement thereof toward and from each. other; means for yieldingly drawing the brake shoes toward each other; means for positively moving the brake shoes away from each other at one end; means operable by motion of said ends of the brake shoes away from each other for effecting a corresponding movement apart. between the opposite ends of the brake shoes; and an automatically adjustable spacer for limiting movement of the brake shoes toward each other to at all times maintain a predetermined. clearance between the braking surfaces of the `shoes and drums, said adjustable spacer comprising, two complementary members, and a connection therebetween allowing movement of said members apart but preventing movement thereof toward each other.

2. In a brake of the character described: a rotatable brake drum; a pair of diametrically opposed; brake shoes inside the drum having surfaces adaptedV for engagement with the drum; a central bearing inside the brake shoes coaxial with the drum; means for spreading the brake shoes at one pair of their adjacent ends; a pair of rings rotatable about said bearing; an abutment on each ring enga'geable with the opposite end of one brake shoe; a connection between each ring and the rst named end of the shoe other than the one engaged by its respective abutment, whereby said rings are rotated in opposite directions by the spreading of the first named ends of the shoes to simultaneously spread the opposite ends of the shoes; means incorporated in said last named connection for automatically taking up play between the rings and the brake shoes; means for yieldingly drawing the second named ends of the shoes together; and an automatically adjustable spacer for limiting the extent to which said second named ends f' of the shoes' are drawn together.

3. In a brake of the character described: aA

'; of diametrically opposed brake shoes inside the a .central bearing inside the brake shoes coaxial with the drum; means for spreading the brake shoes at one pair of their adjacent ends; a pair of rings rotatable about said bearing; an abutment on each ring engageable with thev opposite end of one brake shoe; a connection between each ring and the iirst named end of the shoe other than the one engaged by its respective abutment, whereby said rings are rotated in opposite directions by the spreading of thevi'lrst named ends of the shoes to simultaneously spread the opposite ends of the shoes; means for yieldingly drawing the second named ends of the shoes together; an automatically adjustable spacer for limiting the extent towhich said second named ends of the shoes are drawn together; said automatic spacer comprising, complementary wedge members connected with the brake shoes, andv automatically adjustable means for locking the wedge members again-st relative motion.

4. In a` brake? a rotatable brake drum; ya pair of diametrically opposed brake shoes inside the drum and having surfaces adapted for engagement with the drum; positively acting means between one pair of adjacent ends of the brake shoesy for spreading the same apart; 'a motion transmitting connection between said end of each of said brake -shoes and the opposite end of the other of said brake shoes, whereby movement apart of said iirst designated ends of the brake shoes causes similar movement apart of the opposite ends of the brake shoes; and means for automatically taking up wear and play in said motion transmitting connections.

5. In a brake: a rotatable brake drum; al pair drum and having surfaces adapted for engagement with the drum; positively acting means between one pair of adjacent ends of the brake shoes for spreading the same apart; a motion transmittin-g connection between said end of each of said brake shoes and the opposite end of the other of said brake shoes, whereby movement :apart of sai-d'iirst designated ends of the brake shoes causes similar movement apart of the opposite ends of the brake shoes; and means for automatically taking up wear and play in said motion transmitting connections, said last named means comprising, a part eccentrically mounted and engageable with an abutment on the adjacent portion of the brake shoe, and means yieldingly urging said part in a direction to position its portion having the longest radius toward said abutment.

6. In a brake of the character described:` two kdiametrically opposed brake shoes; means for positively moving one pair of adjacent ends of the brake shoes :away from each other; two rotatable elements, each having an abutment engaging the opposite end'of one ofvsaid brake shoes so that opposite rotation of said elements in direc-tions to lmove their abutments away from each other spreads` said vopposite ends of the brake shoes; driving connections between said rotatable elements and the iirst designated ends of the-brake shoes through which a spreading action at saidV first designated ends of the brake shoes effects such rotation of the rotatable elements; and means incorporated in said driving connection for automatically taking up play between the rotatable elements and the brake shoes.

positively moving one pair of adjacent ends of:

the brake shoes away from each other; twofro-` tatable elements', each having an vabutment 4en-. gaging the opposite end of one of said ,brakeshoes so that opposite rotation of said elements in directions to move their abutments away from each other spreads said opposite ends of the brake shoes; and driving connections between said rotatable elements and the rst designated ends of fthe brake shoes through which a spreading action at said -iirst designated ends of the brake shoes effects such rotation of the rotatable elements, each of said driving connections com. prising, an abutment fixed with respect tothe brake shoe,l an eccentrically mounted member carried by the rotatable element engaging the abutment, and spring means yieldingly urging said eccentrically mounted member in a direc-y tion to at all times urge its portion of `greatest radius towards the abutment.

8. In a brake of the character described: two brake shoes mounted for movement toward and from each other; means yieldingly drawing the brake shoes toward each other; spacing means for limiting the movement of the shoes toward each other and automatically varying the extent to which they approach each other in ac.- cordance with wear on their braking surfaces comprising, complementary wedge members, one connected to each of said brake shoes with a loose connection; and a releasable locking connection for holding the complementary wedge members against relative motion, whereby they extent of play in the loose connections between the wedge members rand the shoes determines the extent to which they approach each other,

Sil'

lOl

said releasable means being releasable upon f movement of the wedge members apart.

9. In a brake of the character described: a

rotatable brake drum; two brake shoes inside the drum having surfaces. adapted for engagement with the drum; means for yieldingly drawing the brake shoes toward eachother and away from the brake drum; a spacer to limit the extent to which the shoes approach each other and rthus determine the clearance between the brake shoes and the drum, said spacer comprising, complementary wedgemembers loosely connected with the brake shoes; and means for releasably securing said wedge members against relative motion, whereby the extent of play in their loose connections with the brake shoes limits the relative motion of the brake shoes toward and from each other, and said locking means being releasable by movement of the wedge members apart to increase the effective length of the spacer as the braking surfaces of the shoes wear. v

10;"In a brake of the character described: a

' brake drum; two brake shoes mounted in the gagement;` a lost motion connection between each' wedgek member andV one brake shoe; a single collary encircling said wedge members, said collar and the portions of the wedge members received therein being tapered so that the wedge members an abutment on one brake shoe, and a part connected with the other brake shoe and bearing against said abutment; and means for taking up play in said connection comprising an element eccentrically rotatable on said part and interposed between said part and the abutment, and a spring yieidingly urging said eccentrically ro tatable element in the direction tending at all times to interpose its portion of greatest radial dimension between said part and said abutment. 10

SYLVESTER F. KARST. FLORIAN F. MANOR. 

